A composite thread comprehensive measuring system and measuring method

Abstract

The application discloses a composite thread comprehensive measuring system and a measuring method, and belongs to the technical field of petroleum pipe measurement. The composite thread comprehensive measuring system comprises a measuring unit, an acquisition unit, a computer data acquisition and processing unit and an automatic feeding frame, a six-axis robot arm is arranged on the computer data acquisition and processing unit, and the six-axis robot arm can drive the measuring unit to rotate and move; the measuring unit is composed of a control module, a high-precision lead screw, a light curtain measuring support and a light curtain measuring assembly, and can perform non-contact measurement on the outer thread of a pipe to be measured; the acquisition unit is composed of a telecentric optical system support, a telecentric optical system and an automatic telescopic rod, and can identify defects and special marks of the thread to be measured. The system can be conveniently installed on a threaded pipe production line, can greatly reduce labor cost and improve measuring efficiency. The measuring method is simple and easy to implement, can provide the overall appearance of the outer thread in less than 60 seconds, obtain full profile parameters, and is suitable for use on a production line.

Description

Technical Field

[0001] This invention belongs to the field of oil pipe metering technology, specifically relating to a composite thread measurement system and method. Background Technology

[0002] Oil well tubing, widely used in oil and gas exploration and development, is made of tapered threads that are tightly connected. The quality of the threads has a significant impact on the quality and lifespan of oil and gas wells. It is essential to strengthen the measurement and inspection of thread parameters (mainly comprehensive parameters such as tightness distance, individual thread parameters, and thread geometry) to ensure that the quality of the oil well tubing threads meets the requirements. This ensures the structural integrity and sealing integrity of the oil well tubing, preventing structural damage under external forces and ensuring that it can withstand long-term effects of internal and external pressure differences under various stress conditions without leakage.

[0003] Existing oil pipe thread measurement methods suffer from the following problems: the latest oil pipe thread standards have raised the requirements for thread processing control, doubling the number of thread parameter inspection items. However, existing testing methods, used for nearly a century, cannot meet the rapid and accurate inspection needs of production lines, significantly increasing product quality risks. Currently, traditional measurements require specialized single-item measuring instruments, and manual operation is time-consuming. To meet the higher requirements for thread parameter inspection efficiency and accuracy, non-contact thread measurement methods are developing rapidly. However, solutions are urgently needed for accurate positioning, improving optical measurement accuracy, and identifying appearance defects (black threads, scratches on special thread sealing surfaces, dents, etc.). Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a composite thread measurement system and method to solve the problems of inaccurate positioning, low measurement accuracy, low efficiency, and inability to identify thread appearance defects in the existing thread measurement process.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention provides a composite thread measurement system, comprising a data acquisition unit, a measurement unit, a computer data acquisition and processing unit, and an automatic feeder. A six-axis robotic arm is mounted on the computer data acquisition and processing unit, with one end of the robotic arm furthest from the computer data acquisition and processing unit connected to the measurement unit. Both the data acquisition unit and the measurement unit are connected to the computer data acquisition and processing unit via data cables. The automatic feeder pushes the thread to be measured into the data acquisition unit to identify defects in the thread. After identification, the automatic feeder pushes the thread to be measured into the measurement unit to obtain the full contour parameters of the thread.

[0007] Preferably, the measurement unit includes a control module, a high-precision lead screw, a light curtain measurement bracket, a measurement baffle, a measurement side plate, and a light curtain measurement assembly. The light curtain measurement bracket is connected to a six-axis robotic arm. The control module is located on the top of the light curtain measurement bracket. The measurement baffle is fixed on the side of the light curtain measurement bracket facing the end face of the thread to be measured. The measurement side plates are located on both sides of the light curtain measurement bracket, forming a 90° angle with the measurement baffle. The light curtain measurement assembly is fixed on the inner wall of the measurement side plate and can emit laser light to collect contour data of the thread to be measured entering the measurement unit. The high-precision lead screw is fixed on both sides of the light curtain measurement bracket and can drive the measurement side plate to move on the high-precision lead screw.

[0008] More preferably, the light curtain measurement assembly includes a light curtain measurement transmitter I, a light curtain measurement transmitter II, a light curtain measurement receiver module II, and a light curtain measurement receiver module I. The light curtain measurement transmitter I and the light curtain measurement receiver module II are sequentially and longitudinally arranged on the inner wall of the measurement side plate, and the light curtain measurement receiver module I and the light curtain measurement transmitter II are sequentially and longitudinally arranged on the inner wall of another measurement side plate. The light curtain measurement receiver module I can receive the laser emitted by the light curtain measurement transmitter I, and the light curtain measurement receiver module II can receive the laser emitted by the light curtain measurement transmitter II.

[0009] More preferably, the distance between the light curtain measuring transmitter I and the light curtain measuring transmitter II is adjustable, with a maximum of 300mm; the distance between the light curtain measuring transmitter I and the light curtain measuring receiving module II, as well as the distance between the light curtain measuring transmitter II and the light curtain measuring receiving module I, can all be adjusted according to the diameter of the thread to be measured.

[0010] Preferably, the acquisition unit includes a telecentric optical system support, an acquisition baffle, acquisition side plates, a telecentric optical system, and an automatic telescopic rod. The automatic telescopic rod is located on the top of the telecentric optical system support and can drive the telecentric optical system support to move longitudinally. The acquisition baffle is located on one side of the telecentric optical system support facing the thread end face to be measured, and the acquisition side plates are located on both sides of the telecentric optical system support, forming a 90° angle with the acquisition baffle. The telecentric optical system acquisition assembly includes a telecentric lens I, a telecentric lens II, and a telecentric lens III. Telecentric lenses II and III are respectively installed on the outer walls of the two acquisition side plates, and telecentric lens I is installed on the inner wall of the acquisition baffle, facing the thread end face to be measured.

[0011] The measurement method of the composite thread measurement system provided by the present invention first calibrates the acquisition unit, then constructs an intelligent detection model for thread joint defects and markings, and uses the constructed intelligent detection model for thread joint defects and markings to identify defects in the thread under test; secondly, the measurement unit is used to locate the thread under test and acquire the tooth profile data of the thread under test; finally, the computer data acquisition and processing unit is used to process the data to obtain the single pitch diameter equation of the thread under test.

[0012] Preferably, the acquisition unit includes a telecentric optical system support, an acquisition baffle, acquisition side plates, a telecentric optical system, and an automatic telescopic rod. The automatic telescopic rod is located on the top of the telecentric optical system support and can drive the telecentric optical system support to move longitudinally. The acquisition baffle is located on the side of the telecentric optical system support facing the thread end face to be measured, and the acquisition side plates are located on both sides of the telecentric optical system support, forming a 90° angle with the acquisition baffle. The telecentric optical system acquisition assembly includes a telecentric lens I, a telecentric lens II, and a telecentric lens III. Telecentric lenses II and III are respectively installed on the outer walls of the two acquisition side plates, and telecentric lens I is installed on the inner wall of the acquisition baffle, facing the thread end face to be measured.

[0013] The specific calibration method is as follows: A standard size is fixed using a standard instrument, and the size is compared with the size measured by the acquisition component of the telecentric optical system to obtain the scaling factor of the telecentric lens.

[0014]

[0015] Where, γ 7x γ is the scaling factor of telecentric lens I in the X direction; 7z γ is the scaling factor of telecentric lens I in the Z direction; 8x γ is the scaling factor of telecentric lens II in the X direction; 8y γ is the scaling factor of telecentric lens II in the Y direction; 9x γ is the scaling factor of telecentric lens III in the X direction; 9y D is the scaling factor of telecentric lens III in the Y direction; D is the outer diameter of the standard; L is the tooth width of the standard; D c7x D is the outer diameter of telecentric lens I measured in the X direction; c7z D is the outer diameter of telecentric lens I measured in the Z direction; c8x L is the outer diameter of telecentric lens II measured in the X direction; c8y D is the tooth width measured in the Y direction for telecentric lens II; c9x L is the outer diameter of the telecentric lens III measured in the X direction. c9y The tooth width is measured in the Y direction for telecentric lens III.

[0016] Preferably, the specific method for defect identification is as follows: the detected features are converted into feature points, lines or surfaces with pixel coordinates using the constructed intelligent detection model of threaded joint defects and markings. Then, a length threshold is set according to the feature extraction requirements, and features that are greater than or less than the threshold are extracted or removed. Finally, the length and position of the corresponding black buckle, defect mark or triangle mark are calculated based on the length of the feature line segment.

[0017] The conversion method is as follows: the coordinates measured by the telecentric optical system acquisition component in the acquisition unit on the feature line segment are (X... PY P Z P The coordinates in the X and Z directions can be obtained from the scale interval between each point on the feature line segment and the origin, while the coordinates in the Y direction can be obtained from the following geometric relationship:

[0018]

[0019]

[0020] The coordinates of each point on the feature line segment are obtained as follows:

[0021]

[0022] The length of the feature line segment is:

[0023]

[0024] Preferably, the positioning steps are as follows: a laser light curtain is sent through the light curtain transmitter in the measurement unit, the light curtain receiving module receives the tooth profile of the thread to be measured, and the light curtain measuring component is driven to move along the axis of the thread to be measured on the high-precision lead screw to obtain the complete thread profile data of the thread to be measured, and obtain the spatial coordinates of each point on the thread profile.

[0025] When there is a relative offset between the thread under test and the light curtain measuring component in the X and Z directions, only the relative offset between the thread and the light curtain measuring component in the Y direction needs to be adjusted. In the Y direction, the angle α that the light curtain measuring component needs to be adjusted is:

[0026]

[0027] Among them, S i T is the pitch of the i-th thread obtained from the positioning measurement of the thread to be tested; i It is the standard pitch of the i-th thread of the thread to be tested.

[0028] Preferably, the data processing method is as follows: the equations of each tooth lateral line are obtained by the computer data acquisition and processing unit, and the equations are as follows:

[0029] f(G i )=k i x+b i i = 1, 2, ..., n;

[0030] Where, k i It is the slope of the flank line obtained by fitting the thread flank point; b i It is the intercept of the flank line obtained by fitting the thread flank point; i represents the i-th flank.

[0031] Let the equations of each individual median diameter be:

[0032] f(D i ) = h i x+c i ;

[0033] Among them, h i It is the slope of a single median diameter; c i It is the single median intercept; i represents the lateral aspect of the i-th tooth;

[0034] The intersection point (x) is obtained when a single median diameter line intersects with the lateral line. gi y gi );

[0035]

[0036] According to the definition of a single median diameter, we can obtain:

[0037]

[0038]

[0039] ···

[0040]

[0041]

[0042] Get h i and c i This yields the complete equation for a single median diameter.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] This invention provides a composite thread measurement system that uses a measuring unit to measure the external thread of the oil pipe under test, obtaining the full profile parameters of the thread. This includes key parameters specified in standards such as taper, ellipticity, thread height, pitch, flank angle, and pitch diameter. It can also measure other dimensions not limited to the above parameters according to the needs of special products. The data acquisition unit identifies common manufacturing defects (black-top threads, sealing surface damage, etc.) and can also identify special markings on the pipe (such as triangular markings, inkjet coding, etc.). This system can be easily installed on threaded pipe production lines. Real-time thread measurement data can be transmitted to the thread processing equipment to calculate the required tool adjustment, statistically control tool calibration, and maintain acceptable tolerances during production. This significantly reduces labor costs and improves measurement efficiency.

[0045] Furthermore, the measurement unit, consisting of a control module, a high-precision lead screw, a light curtain measurement bracket, and a light curtain measurement assembly, can perform non-contact measurement of the thread under test. Compared with other non-image measurement methods, there is no wear and tear on the probe or measuring tool. Compared with other laser measurement methods, the light curtain measurement projection imaging method avoids light scattering, diffraction, etc., greatly reducing the work of image recognition and processing and improving measurement efficiency.

[0046] Furthermore, the laser beam width of the light curtain measuring transmitter is 40mm, and the measurement range can meet the tooth profile of most oil pipe threads.

[0047] This invention provides a measurement method for a composite thread measurement system. This method can provide the overall shape of the external thread and obtain the full profile parameters of the thread in less than 60 seconds. The measurement method is simple and easy to implement, highly versatile and has high calibration accuracy. It is suitable for on-site calibration and can be applied to thread production lines.

[0048] Furthermore, this method utilizes the length and width dimensions of the standard and the measurement dimensions of the telecentric lens to obtain the scaling factor for the acquisition system calibration, so that the acquisition unit is not affected by the position of the calibration reference object and the initial values ​​of the calibration parameters.

[0049] Furthermore, for single pitch diameter and defect identification of threads, the designed single pitch diameter-specific algorithm and the quantitative algorithm for defect identification can improve the relative solution accuracy.

[0050] Furthermore, to address the issue of uncertain relationship between the coordinate system of the measuring unit and the robot itself and the position of the thread to be measured, a positioning method is designed to compensate for the angular offset of the measuring unit. The designed fast angular offset control compensation algorithm can provide feedback to provide control compensation coordinates and move within a small range in the closed loop at the end, thereby effectively improving the positioning accuracy. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the measurement system of the present invention;

[0052] Figure 2 For the present invention Figure 1 Left view of part A in the middle;

[0053] Figure 3 This is a calibration diagram of the telecentric lens I of the present invention;

[0054] Figure 4 This is a schematic diagram illustrating the calibration of telecentric lenses II and III of the present invention;

[0055] Figure 5 This is a feature segment on the thread to be tested according to the present invention;

[0056] Figure 6This is a geometric diagram showing the relationship between the Y-direction coordinates and the X-direction coordinates of the present invention.

[0057] Figure 7 This is a diagram showing the positional relationship between the thread to be measured and the light curtain measuring component of this invention.

[0058] Figure 8 This is a mathematical diagram illustrating the working principle of the present invention.

[0059] Figure 9 This is a diagram of the median diameter of the median meridian f(D1) of this invention.

[0060] The components are as follows: 1-Light curtain measurement transmitter I; 2-Light curtain measurement receiver module II; 3-Light curtain measurement transmitter II; 4-Light curtain measurement receiver module I; 5-Control module; 6-High-precision lead screw; 7-Measurement baffle; 8-Telecentric lens I; 9-Telecentric lens II; 10-Telecentric lens III; 11-Telecentric optical system bracket; 12-Automatic telescopic rod; 13-Automatic feeding rack; 14-Six-axis robotic arm; 15-Computer data acquisition and processing unit; 16-Standard; 17-Light curtain measurement bracket; 18-Thread to be measured; 19-Measurement side plate; 20-Acquisition baffle; 21-Acquisition side plate. Detailed Implementation

[0061] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0062] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0063] The present invention will now be described in further detail with reference to the accompanying drawings:

[0064] See Figure 1The present invention provides a composite thread measurement system, comprising a measurement unit, a data acquisition unit, a computer data acquisition and processing unit 15, and an automatic feeder 13. A six-axis robotic arm 14 is mounted on the computer data acquisition and processing unit 15. The end of the six-axis robotic arm 14 furthest from the computer data acquisition and processing unit 15 is connected to the measurement unit. The six-axis robotic arm 14 can drive the measurement unit to rotate and move in all directions.

[0065] The measurement unit consists of a control module 5, a high-precision lead screw 6, a light curtain measurement bracket 17, a measurement baffle 7, a measurement side plate 19, and a light curtain measurement assembly. A six-axis robotic arm 14 is connected to the light curtain measurement bracket 17. Figure 2 There are two control modules 5, both located on the top of the light curtain measurement bracket 17. The control modules 5 are connected to the light curtain measurement assembly via control wires and can drive the light curtain measurement assembly to move on the high-precision lead screw 6. A measurement baffle 7 is fixed on the side of the light curtain measurement bracket 17 facing the end face of the thread 18 to be measured, and can fix the high-precision lead screw 6. There are two measurement side plates 19, respectively located on both sides of the light curtain measurement bracket 17, forming a 90° angle with the measurement baffle 7. The light curtain measurement assembly is fixed on the inner wall of the measurement side plates 19. The measurement side plates 19 have pre-drilled through holes, and two high-precision lead screws 6 are respectively fixed on both sides of the light curtain measurement bracket 17, able to pass through the pre-drilled through holes in the measurement side plates 19, driving the measurement side plates 19 to move. The high-precision lead screw 6 moves; the light curtain measurement assembly includes a light curtain measurement transmitter I1, a light curtain measurement transmitter II3, a light curtain measurement receiver module II2, and a light curtain measurement receiver module I4. The light curtain measurement transmitter I1 and the light curtain measurement receiver module II2 are arranged longitudinally on the inner wall of one measurement side plate 19, and the light curtain measurement receiver module I4 and the light curtain measurement transmitter II3 are arranged longitudinally on the inner wall of another measurement side plate 19. The light curtain measurement receiver module I4 can receive the laser emitted by the light curtain measurement transmitter I1, thereby acquiring the upper tooth profile of the thread 18 to be measured. The light curtain measurement receiver module II2 can receive the laser emitted by the light curtain measurement transmitter II3, thereby acquiring the lower tooth profile of the thread 18 to be measured.

[0066] The acquisition unit consists of a telecentric optical system support 11, an acquisition baffle 20, acquisition side plates 21, a telecentric optical system, and an automatic telescopic rod 12. The automatic telescopic rod 12 is located on top of the telecentric optical system support 11 and can drive the telecentric optical system support 11 to move longitudinally. It can automatically retract after the acquisition work is completed. The acquisition baffle 20 is located on one side of the telecentric optical system support 11 facing the end face of the thread 18 to be measured. There are two acquisition side plates 21, which are respectively located on both sides of the telecentric optical system support 11, forming a 90° angle with the acquisition baffle 20. The telecentric optical system acquisition assembly includes three telecentric lenses, namely telecentric lens I 8, telecentric lens II 9, and telecentric lens III 10. Telecentric lens II 9 and telecentric lens III 10 are respectively mounted on the outer walls of the two acquisition side plates 21, and telecentric lens I 8 is mounted on the inner wall of the acquisition baffle 20, facing the end face of the thread 18 to be measured.

[0067] The automatic feeder 13 can push the thread 18 to be tested into the acquisition station of the acquisition unit (the space formed by the telecentric optical system bracket 11, the acquisition baffle 20 and the acquisition side plate 21) and the measurement station of the measurement unit (the space formed by the light curtain measurement bracket 17, the measurement baffle 7 and the measurement side plate 19). Both the acquisition unit and the measurement unit are connected to the computer data acquisition and processing unit 15 via data cables. The data acquired by the acquisition unit and the data measured by the measurement unit can be transmitted to the computer data acquisition and processing unit 15 for processing via data cables and displayed through a grating.

[0068] The distance between the light curtain measuring transmitter I1 and the light curtain measuring transmitter II3 can be adjusted, but should not exceed 300mm to meet the measurement accuracy requirements. The distance between the light curtain measuring transmitter I1 and the light curtain measuring receiving module II2, and the distance between the light curtain measuring transmitter II3 and the light curtain measuring receiving module I4, can be adjusted according to the diameter of the thread 18 to be measured.

[0069] The present invention provides a measurement method for a composite thread measurement system, the steps of which are as follows:

[0070] I. Preparatory work before measurement

[0071] 1. Calibration work:

[0072] The three telecentric lenses were calibrated using standard instrument 16. The calibration method is as follows: Figure 3 and Figure 4 As shown, the standard size is fixed using standard device 16, and the size measured by the telecentric lens is compared to obtain the scaling factors of the three telecentric lenses:

[0073]

[0074] γ 7x γ is the scaling factor of telecentric lens I8 in the X direction; 7zγ is the scaling factor of telecentric lens I8 in the Z direction; 8x γ is the scaling factor of telecentric lens II9 in the X direction; 8y γ is the scaling factor of telecentric lens II9 in the Y direction; 9x γ is the scaling factor of the telecentric lens Ⅲ10 in the X direction; 9y D is the scaling factor of telecentric lens Ⅲ10 in the Y direction; D is the outer diameter of standard 16; L is the tooth width of standard 16; D c7x D is the outer diameter of the telecentric lens I8 measured in the X direction; c7z D is the outer diameter of the telecentric lens I8 measured in the Z direction; c8x L is the outer diameter of the telecentric lens II9 measured in the X direction. c8y D is the tooth width measured in the Y direction for the telecentric lens II9; c9x L is the outer diameter of the telecentric lens Ⅲ10 measured in the X direction. c9y The tooth width of the telecentric lens Ⅲ10 measured in the Y direction.

[0075] 2. Defect and identifier feature extraction and machine learning training:

[0076] Collect images of thread surfaces with typical features, such as black threads, dents, scratches, and trapezoidal triangular markings, and name these features Lab. i A training dataset was built, and the collected images of the thread side and end faces were stored in the computer data acquisition and processing unit 15. According to Lab... i The appearance features are used to label images in the dataset. A deep convolutional network model for object detection is built using TensorFlow, PyTorch, PaddlePaddle, or other deep learning frameworks. The model consists of a backbone network and an object detection module. The backbone network, composed of a deep convolutional neural network, is mainly used for image feature extraction. The object detection module consists of a region generator, localization, and classification / regression network, mainly used to generate candidate boxes and optimize the positions of the candidate boxes based on the loss value to make them consistent with the annotation results. After the image is input into the backbone network, it undergoes feature extraction and outputs a feature map with a certain depth. The feature map is then input into the object detection module for candidate box generation and optimization, and finally outputs images with candidate boxes bearing category labels. The deep object detection network model is trained using the constructed dataset. The accuracy of the model is evaluated using test data. Training is completed when the total loss of the model decreases below a critical value. The trained model is stored in the computer data acquisition and processing unit 15, completing the construction of the intelligent detection model for threaded joint defects and markings.

[0077] II. Measurement

[0078] 1. Defect identification of the thread under test:

[0079] The thread 18 to be tested is fed to the acquisition station of the acquisition unit by the automatic feeder 13. The trained intelligent detection model is then used to intelligently identify the thread 18 to be tested. The model will identify any possible Lab errors. i Features are drawn using rectangular detection boxes with corresponding labels. The detected features are transformed, and the coordinates of the feature line segments measured by the telecentric lens are (X... P Y P Z P The coordinates in the X and Z directions can be obtained from the scale interval between each point on the feature line segment and the origin. The coordinates in the Y direction, being coordinates of a circular arc projection, cannot be directly used. The Y-direction coordinates can be obtained from the following geometric relationships:

[0080]

[0081]

[0082] The coordinates of each point on the feature line segment are obtained as follows:

[0083]

[0084] The length of the feature line segment is:

[0085]

[0086] The system calculates feature points, lines, and surfaces with pixel coordinates. Length thresholds can be set according to feature extraction requirements. Features that are greater than or less than the threshold are extracted or removed. Finally, the system calculates the length and location of black leather buckles, defect marks, triangle markers, etc., corresponding to the calculated features.

[0087] Example 1: Suppose a characteristic segment P is measured on the thread, such as... Figure 5 Its length needs to be calculated.

[0088] The coordinates of the line segment measured by the telecentric lens are (X) P Y P Z P The coordinates in the X and Z directions can be obtained from the scale interval between each point on line segment P and the origin. The coordinates in the Y direction, being coordinates of a circular arc projection, cannot be directly used. Figure 6 The Y-coordinate can be obtained from the following geometric relationships:

[0089]

[0090]

[0091] The coordinates of each point on the line segment are obtained as follows:

[0092]

[0093] The length of line segment P is:

[0094]

[0095] 2. Light curtain measurement and positioning:

[0096] After defect identification, the automatic telescopic rod 12 retracts the acquisition unit above the workstation, and the automatic feeder 13 pushes the thread to be tested 18 into the measurement station of the measurement unit. Before measurement, positioning is performed. Since the position of the feeder 13 is fixed, the six-axis robotic arm 14 can perform initial positioning of the thread to be tested 18 based on the position of the feeder 13. Precise positioning is then performed to ensure measurement accuracy. The light curtain transmitter sends a laser light curtain. The laser beam width of the light curtain measurement transmitter is 40mm. After passing through the contour of the thread to be tested 18, the light curtain receiving module receives the tooth profile contour of the thread to be tested 18. The light curtain measurement assembly has one set of light curtain measurement transmitters and one set of light curtain measurement receiving modules at the top and bottom, respectively acquiring the upper and lower tooth profile contours of the thread to be tested 18. The light curtain measurement assembly is driven to move along the axis of the thread to be tested 18 on the high-precision lead screw 6 to obtain complete thread profile data of the thread to be tested 18. Define a virtual pitch diameter M (defined as the diameter of an imaginary cylinder passing through the point where the widths of the grooves and ridges on the thread profiles are equal). The widths P1, P2, P3, ... P' obtained by M through each thread profile are also defined. n The width of each thread profile in the lower half of the pipe profile is compared with the corresponding reference thread width (obtained from the production drawing of the pipe thread to be tested). Similarly, a virtual pitch diameter line M' can be set in the lower half of the thread profile to compare the width of each thread profile in the lower half with the width of the reference thread profile. Figure 7 As shown, the relative offset between the thread and the light curtain measuring component in the X and Z directions does not affect the accuracy of acquiring the thread profile. Only the relative offset between the thread and the light curtain measuring component in the Y direction needs to be adjusted.

[0097] In the Y direction, the angle α that the light curtain measurement component needs to be adjusted is:

[0098]

[0099] Among them, S i T is the pitch of the i-th thread obtained from the positioning measurement of the thread to be tested; i It is the standard pitch of the i-th thread of the thread to be tested (obtained from the design drawings).

[0100] 3. Light curtain measurement of threads:

[0101] After positioning, the measurement of the complete thread profile obtained by moving the light curtain measuring component on the high-precision lead screw 6 is called a complete measurement. The thread profile obtained from the first complete measurement is a set A. iThe data will drive the six-axis robotic arm 14 to rotate the light curtain measuring component counterclockwise (or clockwise, but subsequent operations must be consistent with the direction of this rotation) by a certain angle along the thread ring. The smaller the angle, the more data of the measured contour, and the higher the accuracy of restoring the three-dimensional dimensions of the thread. However, the data processing is more complex and the efficiency is relatively low. Therefore, it can be set according to the requirements when applying it.

[0102] Furthermore, to ensure measurement efficiency, a three-stage rotational scanning measurement can be set. The light curtain measurement transmitter I1 scans the upper portion of the thread profile, and the light curtain measurement receiver module I4 collects the upper profile data. Simultaneously, the light curtain measurement transmitter II3 scans the lower portion of the thread profile, and the light curtain measurement receiver module II2 collects the lower profile data. Therefore, with a rotation angle of 60°, the upper thread profile obtained from the first measurement is a set of A0 data, and the lower thread profile obtained is a set of A... 180 The data, taken by rotating 60° counterclockwise (or clockwise) along the thread ring, yields the upper tooth profile profile of a set A. 60 The data yielded a set of A tooth profiles for the lower part of the tooth shape. 240 The data is then taken by rotating the threaded ring 60° counterclockwise (or clockwise) for a third measurement. The resulting upper tooth profile is a set A. 120 The data yielded a set of A tooth profiles for the lower part of the tooth shape. 300 Data. After three scans, the entire thread profile is captured. Calculations based on these six sets of data can significantly reduce data processing complexity and improve measurement efficiency.

[0103] Furthermore, when the dimensions of the threaded part under test deviate more and more from the nominal value, compensation can be triggered without waiting for it to approach the tolerance limit.

[0104] After the light curtain measurement component acquires all the data, it transmits it to the computer data acquisition and processing unit 15 via a data cable for processing. The entire thread profile is displayed on the grating on the computer data acquisition and processing unit 15, such as... Figure 8 As shown. The length of the grating is the standard length, and the accuracy is the resolution of the measurement system. The spatial coordinates of each point on the thread profile can be obtained based on its positional relationship with the established coordinate origin and the number of gratings passed through. Since the thread pitch diameter is highly correlated with other important parameters of the thread and the thread assembly tightness, determining a single pitch diameter line can directly reflect the overall thread situation.

[0105] The specific steps are as follows: After measuring the spatial coordinates of each point on the thread profile 18 to be measured, the equations of each thread flank are obtained by the computer data acquisition and processing unit 15:

[0106] f(G i )=k i x+bi i = 1, 2, ..., n;

[0107] Where, k i It is the slope of the flank line obtained by fitting the thread flank point; b i It is the intercept of the flank line obtained by fitting the thread flank point; i represents the i-th flank.

[0108] Let the equations of each individual median diameter be:

[0109] f(D i ) = h i x+c i ;

[0110] Among them, h i It is the slope of a single median diameter; c i It is the single median intercept; i represents the lateral aspect of the i-th tooth;

[0111] The intersection point (x) is obtained when a single median diameter line intersects with the lateral line. gi y gi );

[0112]

[0113] Based on the definition of a single pitch diameter line (a line segment passing through the points where the widths of the grooves and ridges on the thread profile are equal, i.e., the distance between all intersection points is equal), we can obtain:

[0114]

[0115]

[0116] ···

[0117]

[0118]

[0119] Get h i and c i This yields the complete equation for a single median diameter.

[0120] Taking the first median diameter f(D1) as an example, the median diameter is as follows: Figure 9 As shown, we can obtain:

[0121]

[0122]

[0123] With only two unknowns in the two equations, we can find h1 and c1, and then successively find h2, c2, ..., h i c iThen, the equation for a single median diameter is obtained.

[0124] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A composite thread measurement system, characterized in that, The system includes a data acquisition unit, a measurement unit, a computer data acquisition and processing unit (15), and an automatic feeder (13). The computer data acquisition and processing unit (15) is equipped with a six-axis robotic arm (14), and the end of the six-axis robotic arm (14) away from the computer data acquisition and processing unit (15) is connected to the measurement unit. Both the data acquisition unit and the measurement unit are connected to the computer data acquisition and processing unit (15) via data cables. The automatic feeder (13) can push the thread to be tested (18) into the data acquisition unit to identify the defects of the thread to be tested (18). After the identification is completed, the automatic feeder (13) can push the thread to be tested (18) into the measurement unit to obtain the full contour parameters of the thread to be tested (18). The measurement unit includes a control module (5), a high-precision lead screw (6), a light curtain measurement bracket (17), a measurement baffle (7), a measurement side plate (19), and a light curtain measurement assembly. The light curtain measurement bracket (17) is connected to a six-axis robotic arm (14). The control module (5) is located on the top of the light curtain measurement bracket (17). The measurement baffle (7) is fixed on one side of the light curtain measurement bracket (17) facing the end face of the thread (18) to be measured. The measurement side plate (19) is located on both sides of the light curtain measurement bracket (17) and forms a 90° angle with the measurement baffle (7). The light curtain measurement assembly is fixed on the inner wall of the measurement side plate (19) and can emit lasers to collect contour data of the thread (18) to be measured entering the measurement unit. The light curtain measurement assembly includes a light curtain measurement transmitter I (1), a light curtain measurement transmitter II (3), a light curtain measurement receiving module II (2), and a light curtain measurement receiving module I (4). The light curtain measurement transmitter I (1) and the light curtain measurement receiving module II (3) are arranged longitudinally on the inner wall of the measurement side plate (19) in sequence. The light curtain measurement receiving module I (4) and the light curtain measurement transmitter II (3) are arranged longitudinally on the inner wall of another measurement side plate (19) in sequence. The light curtain measurement receiving module I (4) can receive the laser emitted by the light curtain measurement transmitter I (1), and the light curtain measurement receiving module II (2) can receive the laser emitted by the light curtain measurement transmitter II (3). The high-precision lead screw (6) is fixed on both sides of the light curtain measurement bracket (17) and can drive the measurement side plate (19) to move on the high-precision lead screw (6).

2. The composite thread measurement system as described in claim 1, characterized in that, The distance between light curtain measurement transmitter I (1) and light curtain measurement transmitter II (3) can be adjusted, with a maximum of 300 mm.

3. The composite thread measurement system as described in claim 1, characterized in that, The distance between the light curtain measuring transmitter Ⅰ (1) and the light curtain measuring receiver Ⅱ (2), as well as the distance between the light curtain measuring transmitter Ⅱ (3) and the light curtain measuring receiver Ⅰ (4), can be adjusted according to the diameter of the thread (18) to be measured.

4. A composite thread measurement system as described in any one of claims 1 to 3, characterized in that, The acquisition unit includes a telecentric optical system bracket (11), an acquisition baffle (20), an acquisition side plate (21), a telecentric optical system, and an automatic telescopic rod (12). The automatic telescopic rod (12) is located on the top of the telecentric optical system bracket (11) and can drive the telecentric optical system bracket (11) to move longitudinally. The acquisition baffle (20) is located on one side of the telecentric optical system bracket (11) facing the end face of the thread (18) to be tested. The acquisition side plate (21) is located on both sides of the telecentric optical system bracket (11) and forms a 90° angle with the acquisition baffle (20). The telecentric optical system acquisition component includes a telecentric lens I (8), a telecentric lens II (9), and a telecentric lens III (10). The telecentric lens II (9) and the telecentric lens III (10) are respectively installed on the outer walls of the two acquisition side plates (21). The telecentric lens I (8) is installed on the inner wall of the acquisition baffle (20) facing the end face of the thread (18) to be tested.

5. A measurement method based on the composite thread measurement system according to any one of claims 1 to 4, characterized in that, First, the acquisition unit is calibrated, and then an intelligent detection model for thread joint defects and markings is constructed. The constructed intelligent detection model for thread joint defects and markings is used to identify defects in the thread to be tested (18). Second, the measurement unit is used to locate the thread to be tested (18) and collect the tooth profile data of the thread to be tested (18). Finally, the computer data acquisition and processing unit (15) is used to process the data and obtain the single pitch diameter equation of the thread to be tested (18). The acquisition unit includes a telecentric optical system bracket (11), an acquisition baffle (20), an acquisition side plate (21), a telecentric optical system, and an automatic telescopic rod (12). The automatic telescopic rod (12) is located on the top of the telecentric optical system bracket (11) and can drive the telecentric optical system bracket (11) to move longitudinally. The acquisition baffle (20) is located on one side of the telecentric optical system bracket (11) facing the end face of the thread (18) to be tested. The acquisition side plate (21) is located on both sides of the telecentric optical system bracket (11) and forms a 90° angle with the acquisition baffle (20). The telecentric optical system acquisition component includes a telecentric lens I (8), a telecentric lens II (9), and a telecentric lens III (10). The telecentric lens II (9) and the telecentric lens III (10) are respectively installed on the outer walls of the two acquisition side plates (21). The telecentric lens I (8) is installed on the inner wall of the acquisition baffle (20) and faces the end face of the thread (18) to be tested.

6. The measurement method of the composite thread measurement system as described in claim 5, characterized in that, The specific calibration method is as follows: use a standard instrument (16) to fix the standard size, compare it with the size measured by the acquisition component of the telecentric optical system, and obtain the scaling factor of the telecentric lens: (1) Where, γ 7x The scaling factor of telecentric lens I (8) in the X direction; γ 7z The scaling factor of telecentric lens I (8) in the Z direction; γ 8x The scaling factor of telecentric lens II (9) in the X direction; γ 8y The scaling factor of telecentric lens II (9) in the Y direction; γ 9x The scaling factor of telecentric lens Ⅲ (10) in the X direction; γ 9y D is the scaling factor of telecentric lens Ⅲ (10) in the Y direction; D is the outer diameter of standard (16); L is the tooth width of standard (16); D c7x D is the outer diameter of telecentric lens I (8) measured in the X direction; c7z D is the outer diameter of telecentric lens I (8) measured in the Z direction; c8x The outer diameter of telecentric lens II (9) measured in the X direction; L c8y D is the tooth width measured in the Y direction for telecentric lens II (9); c9x The outer diameter of the telecentric lens III (10) measured in the X direction; L c9y The tooth width of telecentric lens Ⅲ (10) measured in the Y direction.

7. The measurement method of the composite thread measurement system as described in claim 6, characterized in that, The specific method for defect identification is as follows: the constructed intelligent detection model for threaded joint defects and markings is used to convert the detected features into feature points, lines or surfaces with pixel coordinates. Then, a length threshold is set according to the feature extraction requirements, and features that are greater than or less than the threshold are extracted or removed. Finally, the length and position of the corresponding black buckle, defect mark or triangle mark are calculated based on the length of the feature line segment.

8. The measurement method of the composite thread measurement system as described in claim 7, characterized in that, The transformation is achieved as follows: the telecentric optical system acquisition component in the acquisition unit measures the coordinates on the feature line segment as (X... P Y P Z P The coordinates in the X and Z directions can be obtained from the scale interval between each point on the feature line segment and the origin, while the coordinates in the Y direction can be obtained from the following geometric relationship: The coordinates of each point on the feature line segment are obtained as follows: The length of the feature line segment is: 。 9. The measurement method of the composite thread measurement system as described in claim 8, characterized in that, The positioning steps are as follows: a laser light curtain is sent through the light curtain transmitter in the measurement unit, the light curtain receiving module receives the tooth profile of the thread to be measured (18), and drives the light curtain measuring component to move along the axis of the thread to be measured (18) on the high-precision lead screw (6) to obtain the complete thread profile data of the thread to be measured (18) and obtain the spatial coordinates of each point on the thread profile. When the thread to be tested (18) and the light curtain measuring component are offset relative to each other in the X and Z directions, the relative offset between the thread and the light curtain measuring component in the Y direction is adjusted. In the Y direction, the angle α of the light curtain measuring component is adjusted as follows: Among them, S i T is the pitch of the i-th thread obtained from the positioning measurement of the thread to be tested; i It is the standard pitch of the i-th thread of the thread to be tested.

10. The measurement method of the composite thread measurement system as described in claim 9, characterized in that, The data processing method is as follows: the equations of each tooth lateral line are obtained by the computer data acquisition and processing unit (15), and the equations are as follows: Where, k i It is the slope of the flank line obtained by fitting the thread flank point; b i It is the intercept of the flank line obtained by fitting the thread flank points; i represents the i-th flank. Let the equations of each individual median diameter be: Among them, h i It is the slope of a single median diameter; c i It is the single median intercept; i represents the lateral aspect of the i-th tooth; The intersection point (x) is obtained when a single median diameter line intersects with the lateral line of the tooth. gi y gi ); According to the definition of a single median diameter, we can obtain: Get h i and c i This yields the complete equation for a single median diameter.

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